Evolution of the Internet has caused an enormous increase in the use of digital media. Internet has become the primary channel for transmitting digital data to distant locations. A digital media such as digital audio, digital video, and digital images can be easily created, edited, converted and delivered using a computer connected to the Internet. Consequently, digital medium has faced problems of piracy as described next.
Pirates now have easy access to the tools necessary to make illegal copies and unauthorized use of proprietary material contained in a digital medium. For example, music is rampantly pirated in the form of MP3 format files, which are easily created and illegally proliferated with a minimal skill level. For example, a pirate can copy a piece of music stored on a compact disk (CD) and convert it into MP3 format files using generic and freely available tools. The pirate then uses a peer-to-peer file-sharing network to freely distribute such MP3 format files on a worldwide scale. Thus, there is a need for a mechanism by which the rightful owner of an electronic content can robustly control copying, secure copyrights, prevent illegal distribution, and provide easy tracking of pirated materials. Many techniques are known for content protection purposes. An overview of the field of fingerprinting as for content security applications is discussed next.
Methods for controlling use of electronic materials exist. One such family of methods is termed as “media fingerprinting”. Fingerprinting refers to the technology that extracts a fingerprint of and from a source medium. The extracted fingerprint may then be stored on a variety of different storage mechanisms like databases or data-stores for subsequent use in tracking copies of the source medium. A fingerprint of a medium is a small and unique mark or characteristic of the medium from which the mark is generated or extracted from. The fingerprint is small in size as compared to the source media datastream. A given fingerprint is also unique as compared to all other fingerprints in the database(s) or data-stores. It usually can be used to identify the source medium. It can also be used to determine the originality of a piece of medium. In general, the criteria for a successful media fingerprinting include uniqueness as well as robustness, i.e., robustness against common processing noise. Desirable features of a fingerprint in the context of various operations carried out on the medium are described next.
The fingerprint should not change after a given medium undergoes processing such as compression, scaling, blurring, reprinting, etc. These common signal-processing tasks often do not alter the overall structure or the overall appearance of the medium data; however, each such processing task would alter the details of the medium data to various degrees. Therefore, there is a need for a robust representation of medium content, so that the representation is invariant against common processing noises, and can preserve the fingerprint under any common signal processing. Security aspects of fingerprinting are described next.
At times, it is also desirable to have survivability towards certain intentional attacks. That is, ideally, any processing on the medium that does not change the perceptual content of the medium should not change the fingerprint. For instance, a fingerprint of a song in a digital form should not change without distorting the music. Media fingerprinting is an effective and easy to implement technique for protecting electronic content stored on a digital medium. There is a need for an implementation of a fingerprinting method, which is commercially viable, low cost, and operates in a real-time mode. Various known approaches to fingerprinting and their limitations are as described next.
One approach toward fingerprinting embeds fingerprint data in a source medium and then uses a decoding medium to recover the original medium. This approach is often termed as “active fingerprinting”. For example, U.S. Pat. No. 5,859,920 to Daly et al. creates an encoded source image embedded with source data. Active fingerprint typically accompanies the source media data; hence, there is no need to connect to a network for fingerprint verification. The drawback, however, is that when the source medium is altered, the fingerprint can easily get lost. It is sometimes desirable to transform the source medium in a content preserving way in order to adapt to different application requirements and networking conditions. For instance, compression and transcoding are among the most frequently used transformations.
Another approach is termed as “passive fingerprinting”. Passive fingerprinting refers to the system and method that saves the extracted fingerprint in a remote secure server. Technologies dealing with passive fingerprints are known in the art. For example, U.S. Pat. No. 5,918,223 to Blum, et al., discloses forming a vector of features from audio files. However, this approach is not directed to compressed media.
A digital medium is often stored, processed or transmitted in a variety of compressed formats. Compressed formats for contents stored on digital media are preferred due to huge sizes of electronic media files. Storing and processing such huge files is a complex and slow process. Thus, there is a need for an apparatus and method for authenticating and securing electronic media existing in the compressed format. Such apparatus and method should operate in a speedy manner to process large media file sizes for real-time or streaming applications.
Therefore, is a need for a robust fingerprinting apparatus and method. The fingerprinting apparatus and method should generate unique fingerprints that are robust against common processing noise. Further, the fingerprint should be able to survive certain intentional attacks.